Diethylamino fluorans

ABSTRACT

A CHROMOGENIC MATERIAL OF NORMALLY COLORLESS FORM IS DISCLOSED, HAVING A STRUCTURAL FORMULA:     XANTHENE   WHEREIN ONE OF R, R1 AND R2 REPRESENTS A CHEMICAL RADICAL FROM A GROUP COMPRISING -CO-R4,-O-R4, AND -CO-O-R4 WHEREIN R4 REPRESENTS HYDROGEN, ARYL RADICALS, AND ALKYL RADICALS; THE REMAINING OTHERS OF R, R1 AND R2 REPRESENT HYDROGEN, HALOGEN, AND ALKYL RADICALS; AND R3 REPRESENTS HYDROGEN AND ALKYL RADICALS HAVING LESS THAN FIVE CARBON ATOMS-SAID MATERIALS ASSUMING A COLORED FORM UPON REACTIVE CONTACT WITH A LWEIS ACID MOLECULE. EXAMPLES INCLUDE 2&#39;&#39;-BENZYLOXY-L&#39;&#39;-DIETHYLAMINOFLOURAN; 6&#39;&#39;-DIETHYLAMINO-2&#39;&#39;-FORMYLFLUORAN; 2&#39;&#39;-CARBOMETHOXY-L&#39;&#39;-DIETHYLAMINOFLUORAN; AND 2&#39;&#39;-BENZOYL-6&#39;&#39;-DIETHYLAMINO-4&#39;&#39;-METHYLFLUORAN. 3-(O=),2&#39;&#39;-R2,3&#39;&#39;-R1,4&#39;&#39;-R,6&#39;&#39;-((R3-)2-N-)SPIRO(PHTHALAN-1,9&#39;&#39;-

CHAO-HAN LIN 3,637,757

DIETHYLAMINO FLUORARN Jan. 25, 1972 Filed Jan. 21, 1969 COATED ON THEREAR WITH MINUTE PRESSURE-RUPTURABLE CAPSULES CONTAINING LIQUID SOLUTIONOF CHROMOGENIC MATERIAL DEVELOPABLE ON CONTACT WITH AN ELECTRON-ACCEPTING MATERIAL OF THE LEWIS- ACID\ TYPE TO COLORED FORM RECEIVINGSURFACE OF UNDERSHEET COATED WITH AN ELECTRON-ACCEPTING MATERIAL OF THELEWIS ACID TYPE FIG 2 INVENTOR CHAO-HAN LIN B EWQXL HIS AGENT UnitedStates Patent flice 3,637,757 Patented Jan. 25, 1972 3,637,757DIETHYLAMINO FLUORANS Chao-Han Lin, Dayton, Ohio, assignor to TheNational Cash Register Company, Dayton, Ohio Filed Jan. 21, 1969, Ser.No. 792,325 Illt. C1. C07(] 21/00 U.S. Cl. 260-6433 3 Claims ABSTRACT OFTHE DISCLOSURE- A chromogenic material of normally colorless form isdisclosed, having a structural formula:

BACKGROUND OF THE INVENTION This invention pertains to chromogeniccompounds for use in pressure sensitive record material and to animproved mark-forming manifold system incorporating these chromogeniccompounds. More specifically, this invention pertains to acyl-, ether-,and ester-substituted dialkylamino fiuorans which have the form ofsubstantially colorless, i.e., White, or slightly colored solids, orapproach being colorless when in liquid solution, but which may beconverted to dark-colored forms upon reactive contact with appropriateacidic material. As used in mark-forming systems, marking in desiredareas on support webs or sheets may be accomplished by effectinglocalized reactive contact between the novel chromogenic material andthe acidic material on or in such a web or sheet, such material beingbrought thereto by transfer, or originally there, in situ--the desiredreactive contact forming darkcolored materials in the intended imageareas.

Pressure-sensitive, mark-forming systems of the prior art include thatdisclosed in application for Letters Patent No. 392,404 (now abandoned),filed Aug. 27, 1964, in the names of Robert E. Miller and Paul S.Phillips, Jr. The above-mentioned patent application provides a markingsystem of disposing on and/or Within sheet support material, mutuallyreactant but unreacted markforming components (at least one component ofwhich is a polymeric material) and a liquid solvent in which each of themark-forming components is solublesaid liquid solvent being present insuch form that is maintained isolated by a pressure-rupturable barrierfrom at least one of the mark-forming components until an application ofpressure causes a breach or rupture of the barrier in the areadelineated by the pressure pattern. The mark-forming components therebyare brought into reactive contact, producing a distinctive mark.

It is an object of this invention to provide new and improved substanceshaving chromogenic properties which may be incorporated in a web orcoated onto the surface of a web to provide a manifolding unit, andwhich are, moreover, useful in carrying out improved methods of markinginvolving reactive contact with a color-activating material to yielddark-colored reaction products in areas where marking is desired.

It is another object of this invention to provide compounds, based uponthe acyl-, ether-, and ester-substituted dialkylamino fluorans disclosedherein which are substantially colorless, or slightly colored offering anew and improved variety of chromogenic characteristics, and yieldingnovel dark-colored substances upon contact with color-activatingmaterials.

It is a further object of this invention to provide a new and improved,normally substantially colorless, chromogenic substances yielding Lewisacid-reacted color products which exhibit improved color stability onexposure to light and improved reproduction capabilities when copied byXerographic or diazo processes.

It is a further object of this invention to provide new and improved,normally substantially colorless, chromogenie substances yieldingcolored reaction products when placed in reactive contact with certainselected Lewis acid materials.

It is a further object of this invention to provide a new and improvedmark-forming system which comprises disposing, within a web or upon thesurface of a web or sheet-support-material, unreacted chromogenicmaterial in a location suitable for subsequent reactive contact with anacidic material to produce dark-colored reaction products, thusproviding means for making marks of desirable color intensity and hue.

In accordance with one feature of this invention, there is provided asubstantially colorless or slightly colored, chromogenic compound havingthe structural formula:

6 diethylamino 2-formylfiuoran having the structural formula:

2'-carbomethoxy-6-diethylaminofiuoran having the structural formula:

2' benzoyl-6'-diethylamino-4'-methylfluoran having the structuralformula:

In accordance with another feature of this invention, a new compositionof matter is disclosed which comprises a dark-colored product ofchemical reaction having a r resonant chemical structure and produced bycontact of a color-activating material with one of the above-mentionedchromogenic compounds. The color-developing or activating material is anacidic substance useful for converting the chromogenic compounds tocolored forms.

The method of marking of this invention, i.e., the method of developinga dark-colored material from substantially colorless or slightly coloredchromogenic compounds, comprises providing a chromogenic compoundselected from among the above-mentioned compounds and bringing suchchromogenic compound into reactive contact with an acidiccolor-activating substance, in areas where marking is desired, toproduce a dark-colored form of the chromogenic compound by the actionthereon of said acidic substance. 40

Acidic materials employed in this invention can be any compound withinthe definition of a Lewis acid, i.e. any electron acceptor. Preferably,acidic organic polymers such as phenolic polymers are employed as theacidic material. The novel chromogenic materials exhibit the ad vantageof improved color stability when they are reacted with such phenolicpolymers. Solution formation of solid particles of the polymericmaterial in a solvent system with the substantially colorlesschromogenic compounds permits penetration of the dark-colored reactionproduct into a porous support sheet, e.g., paper, so that the coloredform of the chromogenic material is absorbed into the body of the sheetand is not merely on the surface of the sheet. The absorption featureprovides protection against erasure of recorded data by attrition of thesurface of a record sheet made in accordance with the present invention.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a diagrammatic representationof a two-sheet unit manifold, in perspective. The bottom surface of theoverlying sheet is supplied on the surface or near the surface With amultiplicity of minute pressure-rupturable microcapsules containing asolution of the novel, substantially colorless, chromogenic component.An acidic component, such as an acid clay or a phenolic polymericmaterial lies Within the lower web or undersheet or upon the uppersurface of the lower web or undersheet. A colored mark is made by theuse of a stylus, a type character, or other pressure-exerting meansapplied to the twosheet unit manifold.

The encapsulated solution is released on the event of rupture of thecapsules in writing operations, as is shown in FIG. 2 FIG. 2 is asectioned view of the two-sheet unit manifold of FIG. 1. The elementsare not to scale and are so-shown in order to more effectively depicttheir interrelation. The released solution is transferred from theoverlying or base-sheet to the receiving surface of'the underlying sheetin conformance with the pressure pattern of the writing operation. Thedrawing shows that the top of the underlying sheet is coated orimpregnated with a material reactant with the chromogenic material,e.g., an acid clay or an acidic phenolic polymer material; and thatcapsules are present on the overlying or base-sheet which capsulescontain a liquid solution of chromogenic material. In another embodimentof the record material, however, the capsules can contain the polymericphenolic material in liquid solution and the receiving surface of theunderlying sheet can be supplied with the chromogenic material. Theimprovement in the system resides in the chromogenic material, whichchromogenic material is the substance of the instant invention.

Referring again to FIG. 1, comprising an overlying or base-sheet havingthe chromogenic material located within or upon the sheet; it ispossible to incorporate the chromogenic material in a solid, crystallinestate in a binder material so that the chromogenic material may betransferred from the overlying sheet, upon the application of pressure,to deposit some of the chromogenic material on the receiving surface ofthe undersheet, which receiving surface carries a color-activatingpolymeric material. Preferably, the chromogenic substance is dissolvedin an appropriate solvent and minute droplets of the solution of thechromogenic material are encapsulated in minute, rupturable, capsules.It is apparent that many other arrangements are possible, includingdifferent configurations and relationships of the solvent and all of themark-forming materials with respect to their encapsulation and locationon the supporting underlying or overlying sheets or webs can beenvisioned. Such arrangements are thoroughly described in theaforementioned application Ser. No. 392,404 (now abandoned) in the namesof Miller et al. and need not be repeated herein.

SUMMARY OF THE INVENTION It is noted that the polymeric mark-formingcomponents should have a common solubility with the chromogenic materialin at least one liquid solvent when the acidreacting material is aphenolic or other acidic organic polymer. It is also noted that in asingle system several chromogenic materials may be used with the same ordifferent polymeric materials. Several polymeric materials can bereactively contacted with a single chromogenic compound or with amixture of chromogenic compounds.

As mentioned above, the solvent can be maintained in physical isolationin minute droplets until such time as it is released by application ofpressure. This may be accomplished by several known techniques, but,preferably, isolation is maintained by encapsulation of individualdroplets of the solvent in a microcapsule according to the proceduresdescribed, for example, in US. Pat. No. 2,712,507, issued July 5, 1955on the application of Barrett K. Green; 2,730,457 issued Jan. 10, 1956on the application of Barrett K. Green and Lowell Schleicher; 2,800,457,issued July 25, 1957 on the application of Barrett K. Green and LowellSchleicher; 2,800,458, issued July 23, 1957 on the application ofBarrett K. Green and Lowell Schleicher; 2,800,458, issued July 23, 1957on the application of Barret K. Green, reissued as Reissue Pat. No.24,899 on Nov. 29, 1960; and 3,041,289, issued June 26, 1962 on theapplication of Bernard Katchen and Robert E. Miller. The microscopiccapsules, when disposed within or upon a supporting web as amultiplicity in contiguous juxtaposition, are rupturable by pressure,such as normal marking pressure found, for example, in writing or typingoperations. I

The material or materials chosen as the wall material for thedroplet-containing microcapsules, in addition to being pressurerupturable, must be inert or unreactive with respect to the intendedcontents of the capsules and the other mark-forming components so thatthe capsule wall material will remain intact under normal storageconditions until such time as it is released by an application ofmarking pressure. Preferred examples of eligible capsule wall materialsinclude gelatin, gum arabic and many others thoroughly described in theaforementioned patents.

For most uses in record material, the capsule size should not exceedabout 50 microns in diameter. Preferably, the capsules should be smallerthan about 15 microns in diameter.

The acidic organic polymeric material useful for developrng the color ofnovel chromogenic compounds in this lnvention include phenolic polymers,phenol acetylene polymers, maleic acid-rosin resins, partially or whollyhydrolyzed styrene-maleic anhydride copolymers and ethylene-maleicanhydride copolymers, carboxy polymethylene and wholly or partiallyhydrolyzed vinylmethylethermalerc anhydride copolymer and mixturesthereof.

More specifically, phenolic polymers found useful include alkyl-phenolacetylene resins, which are soluble in common organic solvents andpossess permanent fusibihty 1n the absence of being treated bycross-linking materials. Another specific group of useful phenolicpolymers are members of the type commonly referred to as novolacs (atype of phenolformaldehyde polymeric material) which are characterizedby solubility in common organic solvents and which are, in the absenceof cross-linking agents, permanently fusible. Resol resins, if they arestill soluble, may be used, though they are subject to change inproperties upon aging. Generally, phenolic polymer material found usefulin practicing this invention is characterized by the presence ofhydroxyl groups and by the absence of groups such as methylol, whichtend to promote infusibility or cross-linking of the polymer, andfurther, by being soluble in organic solvents and relatively insolublein aqueous media. Again, it should be remembered that mixtures of theseorganic polymers and other acidic materials can be employed.

A laboratory method useful in the selection of suitable phenolic resinsis the determination of the infrared absorption pattern. It has beenfound that phenolic resins which undergo absorption in the 32003 500cm.-- region (which is indicative of hydroxyl groups) on the resinmolecules and which do not absorb in the 1600-1700 cm?" region areeligible. This latter absorption region is indicative of desensitizationof hydroxyl groups which densensitization renders such groupsunavailable for reaction with the chromogenic materials.

The preparation of some organic polymeric materials useful forpracticing this invention has been described in Industrial andEngineering Chemistry, vol. 43, pp. 134 to 141, January 1951, and aparticular polymer thereof is described in Example I of US. Pat. No.2,052,- 093, issued to Herbert Honel on Aug. 25, 1936. The preparationof the phenol-acetylene polymers has been described in Industrial andEngineering Chemistry, vol. 41, pp. 73 to 77, January 1949. Thepreparation of maleic anhydride copolymers is described in theliterature, such as, for example, one of the maleic anhydride vinylcpolymers, as disclosed in Vinyl and Related Polymer, by Calvin E.Schildknecht, second printing, published April 1959, by John Wiley &Sons, Incorporated: See pages 65 to 68 (styrene-maleic anhydridecopolymer), 530 to 531 (ethylene-maleic anhydride copolymer), and 628 to630 (vinylmethylether-maleic anhydride copolymer).

When the acidic material used as a mark-forming component in the presentinvention is one of the aforementioned organic polymers, the liquidsolvent chosen must be capable of dissolving it. The solvent may bevolatile or nonvolatile, and a singleor multiple-component solvent maybe used which is wholly or partially volatile. Examples of volatilesolvents useful in practicing the present invention include toluene,petroleum distillate, perchloroethylene, and xylene. Examples ofnonvolatile solvents include high-boiling-point petroleum fractions andchlorinated biphenyls. Generally, the solvent chosen should be capableof dissolving at least about 0.3 percent, by weight, of the chromogenicmaterial, and at least about 3 to 5 percent, by weight, of the acidicpolymeric material to yield an effective reaction. However, in thepreferred system, the solvent should be capable of dissolving an excessof the polymeric material, so as to provide every opportunity forutilization of the chromogenic material and, thus, to assure maximumcoloration at the reaction site.

A further criterion for selection of the solvent is that the solventmust not interfere with the mark-forming reaction. In some instances,the presence of the solvent may be found to interfere with themark-forming reaction or diminish the intensity of the mark, in whichinstances the solvent chosen should be sufiiciently volatile to assureits removal from the reaction site soon after having brought themark-forming components into reactive contact so that the mark-formingreaction can proceed.

Since the mark-forming reaction requires that an intimate mixture of thecomponents be brought about through solution of said components, one ormore of the markforming components can be dissolved in solvent dropletsisolated by encapsulation, the only requirement being that at least oneof the components essential to the markforming reaction be maintainedisolated until the markforming reaction is desired.

In the usual case, the mark-forming components are so chosen as toproduce a mark upon application of pressure to a coated system of sheetsat room temperature (20 to 25 degrees Centigrade). However, the presentinvention also includes a system wherein the solvent component is notliquid at temperatures near room temperature but is liquid and incondition for forming solutions only at elevated temperatures.

The support sheet member on which components of the system are disposedmay comprise a single or a dual sheet assembly. In the case where allcomponents are disposed on a single sheet, the record material isreferred to as a self-contained or autogenous system. Where there mustbe a migration of solvent, with or without the mark-forming component,from one sheet to another, the record material is referred to as atransfer system. (Such a system may also be referred to as a two-foldsystem, in that at least two sheets are required and each sheet includesa component, or components, essential to the mark-forming reaction.)Where an adequate amount of the colored reaction product is produced inliquid or dissolved form on a surface of one sheet, a colored mark canbe recorded on a second sheet by transfer of the colored reactionproduct.

In a preferred case, where microcapsules are employed, they can bepresent in the sheet support material either disposed therethroughout oras a coating thereon, or both. The capsules can be applied to the sheetmaterial as a dispersion in the liquid vehicle in which they weremanufactured, or, if desired, they can be separated from the vehicle andthereafter dispersed in a solution of the acidreacting polymericcomponent (for instance, 30 grams of water and 53 grams of a 1 percent,by weight, aqueous solution of polyvinylmethylether-maleic anhydride) toform a sheet-coating composition in which, because of the inertness ofthe solution and the capsules, both components retain their identity andphysical integrity. When this composition is disposed as a film on thesupport material and dried, the capsules are held therein subject torelease of the contained liquid by rupture of the capsule walls. Thelatter technique, relying on the inertness of the microcapsule and thedispersing medium of the film-forming mark-forming polymeric component,provides a method for preparing a sensitive record material coatinghaving the capsules interspersed directly in a dry film of the polymericmaterial as the film is laid down from solution. A further alternativeis to disperse one or more markforming components, and thechromogenic-material-containing microcapsules in a liquid medium not asolvent for either the mark-forming component or the microcapsules, withthe result that all components of the markforming system may be disposedon or within the support sheet in the one operation. Of course, theseveral components may be applied individually. The capsules can also becoated onto a sheet as a dispersion in a solution of polymeric materialwhich is not necessarily reactive with the capsule-contained solution ofchromogenic materials.

The respective amounts of the several components can be varied accordingto the nature of the materials and the architecture of the recordmaterial unit desired or required. Suitable lower amounts include, inthe case of the chromogenic material, about 0.005 to 0.075 pound perream (a ream in this application meaning five hundred (500) sheets of x38 paper, totalling 3,300 square feet); in the case of the solvent,about 1 to 3 pounds per ream; and in the case of the polymer, about 0.5pound per ream. In all instances, the upper limit is primarily a matterof economic consideration.

The slurry of capsules can be applied to a wet web of paper, forexample, as it exists on the screen of a Fourdrinier paper machine, soas to penetrate the paper web a distance depending on the freeness ofthe pulp and the water content of the web at the point of application.The capsules can be placed directly in or on a paper or support sheet.Not only capsule structures, but continuous films which contain amultitude of microscopic, unencapsulated, droplets for local release inan area subjected to pressure can be utilized. (See, for example, US.Pat. No. 2,299,694 which issued Oct. 20, 1942, on the application ofBarrett K. Green.)

With respect to the acidic organic polymeric component, a solutionthereof in an evaporable solvent can be introduced into an amount ofwater and the resulting mixture can be agitated while the evaporablesolvent is blown off by an air blast. This operation leaves an aque ouscolloidal dispersion slurry of the polymeric material, which may beapplied to finished paper so as to leave a surface residue or the slurrymay be applied to a wet web of paper or at the size-press station of apaper making machine. In another method for making a polymer-sensitizedsheet, the water-insoluble polymer can be ground to a desired orrequired particle size in a ball mill with water, preferably with adispersing agent, such as a small quantity of sodium silicate. If abinder material of hydrophilic properties is ground with the polymericmaterial, the binder itself may act as a dispersant. If desired, anamount of binder material of up to percent, by weight, of the amount ofpolymeric material can be added to the ball-milled slurry ofmaterials-such binder materials being of the paper coating binder class,including, for example, gum arabic, casein, hydroxyethylcellulose, andlatexes (such as styrene-butadiene copolymer). If desired, oilabsorbents in the form of fullers earths may be combined with thepolymeric material particles to assist in retaining, in situ, the liquiddroplets of chromogenic material solution to be transferred to it indata-representing configuration, for the purpose of preventing bleedingof the print.

Another method for applying the chromogenic or polymeric materialindividually to a single sheet of paper is by immersing a sheet of paperin 110 percent, by weight, solution of the material in an evaporablesolvent. Of course, this operation must be conducted individually foreach reactant, because if the other reactant material were present,contact of the reactants would result in a premature coloration over thesheet area. A dried sheet with one component can then be coated with asolution of another component, the solvent of which is a non-solvent tothe already-supplied component.

The polymeric material can also be dissolved in ink composition vehiclesto form a printing ink of colorless character and, thus, may be used tospot-print a proposed record-sheet-unit sensitized for recording, in areactionproduced color in those spot-printed areas, by application of asolution of the chromogenic material. In the case of phenolic polymer, aprinting ink may be made of up to percent, by weight, of the phenolicpolymeric material in a petroleum-based solventthe ink being built to aviscosity suitable for printing purposes. The relative amounts ofreactive, mark-forming, components to be used in practice of thisinvention, are those most convenient and economical amounts consistentwith adequate, desired or required visibility of the recorded data. Theresolution of the recorded data is dependent on, among other things,particle or capsule size, distribution and amount of particles orcapsules, liquid solvent migration, chemical reaction efficiency, andother factors, all of which can be optimized empirically by one skilledin the art. Such factors do not determine the principle of the presentinvention, which invention, in part, relates to means for enabling thebringing into solution contact, by marking pressure, two normally solid,chemically reactive, components dissolved in a common liquid solventcomponent held isolated as liquid droplets. The isolated liquid dropletsare preferably in marking-pressure-rupturable capsules havingpolymeric-film walls, or are isolated, as a discontinuous phase, in acontinuous marking-pressure-rupturable film.

In the color system of this invention the acidic markforming materialreacts with the chromogenic material to effect distinctive colorformation or color change. In a multi-sheet system in which an acidicorganic polymer is employed, it may be desirable to include othermaterials to supplement the polymer reactants. For example, kaolin canbe added to improve the transfer of the liquid and/ or the dissolvedmaterials between the sheets. In addition, other materials such asbentonite, attapulgite, talc, feldspar, halloysite, magnesiumtrisilicate, silica gel, pyrophyllite, zinc sulfate, calcium sulfate,calcium citrate, calcium phosphate, calcium fluoride, barium sulfate andtannic acid can be included.

Various methods known to the prior art and others disclosed in theaforementioned application S.N. 392,404 (now abandoned) in the names ofMiller et al, and in US. patent application S.N. 420,193 in the names ofPhillips et al. and issued as US. Pat. No. 3,455,721 on July 15, 1969can be employed in compositions useful for coating mark-formingmaterials into supporting sheets. An example of the compositions whichcan be coated onto the receiving surface of an underlying sheet of amulti-sheet to react with a capsule coating on the underside of anoverlying sheet is as follows:

Percent Coating composition: by weight Phenolic polymer mixture 17 Papercoating kaolin (white) 57 Calcium carbonate l2 Styrene butadiene latex 4Ethylated starch 8 Gum arabic 2 Having disclosed, generally, the novelchromogenic materials of this invention and preferred methods forutilizing the novel chromogenic materials, in combination with othermaterials, as reactive components in mark-forming record material;examples will now be disclosed wherein preparation of several of thenovel chromogenic materials is described.

9 EXAMPLE 1 Preparation of 2-benzoyloxy-6'-diethylamino fluoran Areaction mixture of 3.1 grams of2-carboxy-4'-diethylamino-2'-hydroxybenzophenone, 2.0 grams ofbenzyloxyphenol, and 30 milliliters of 75 percent, by Weight, aqueoussulfuric acid solution was heated for about 1.5 hours at 95-100 degreescentigrade. The reaction mixture was then poured into about 100milliliters of water and made alkaline to a pH of above about 8 byaddition of dilute, aqueous, sodium hydroxide solution. A precipitatewas thrown down and that precipitate was extracted with benzene. Thebenzene extract was washed 3 times with SO-rnilliliter volumes of 10percent, by weight, aqueous sodium followed by a wash with Water. TheWater-Washed benzene extract was evaporated to dryness to obtain 0.45gram of crude reaction product. The crude product waschromotographically purified over activated alumina. A benzene solutionof the purified reaction product imparted a reddish-purple color topaper coated with a mixture of kaolin and phenolic resin.

EXAMPLE 2 Preparation of 2'-formyl-6-diethylaminofluoran A reactionmixture of 3.1 grams of 2-carboxy-4-diethyl-amino-2-hydroxybenzophenone,1.2 grams of p-hydroxybenzaldehyde, and milliliters of 90 percent, byweight, aqueous sulfuric acid solution was heated for about 1 hour at140-145 degrees centigrade. The reaction mixture was then poured intoabout 0 milliliters of water and made alkaline to a pH of above about 8by addition of dilute, aqueous, ammonium hydroxide solution. Thereaction mixture was extracted by 250 milliliters of benzene and thebenzene extract was Washed with sodium hydroxide solution and then withwater. The reaction product was chromatographically purified overalumina. A benzene solution of the purified reaction product imparted anorange color to paper coated with a mixture of kaolin and phenolicresin.

EXAMPLE 3 Preparation of 2'-carbomethoxy-6-diethylaminofluoran Areaction mixture of 1.6 grams of 2-carboxy-4'-diethylamino 2'hydroxybenzophenone, 0.76 gram of methyl-p-hydroxybenzoate and 20milliliters of percent, by weight, aqueous sulfuric acid solution washeated for about 5 hours at 98-102 degrees centigrade. The reactionmixture was then poured into water and made alkaline to a pH of aboveabout 8 by addition of dilute, aqueous, ammonium hydroxide. The reactionmixture was extracted by benzene, washed and concentrated byevaporation. The crude product was chromatographically purified overalumina. A benzene solution of the purified product imparted an orangecolor to paper coated with a mixture of kaolin and phenolic polymer.

EXAMPLE 4 Preparation of 2-benzoyl-6-diethylamino-4- methylfluoran Areaction mixture of 0.3 gram of2-carboxy-4'-diethylamino-2'-hydroxybenzophenone, 0.2 gram of 4-hydroxy-3-methylbenzo-phenone, and 10 milliliters of '80 percent, by weight,aqueous sulfuric acid solution was heated for about 1 hour at -140degrees centigrade. Reaction product isolation and purification wasconducted as described in the previous examples, above. A benzenesolution of the purified reaction product imparted an orange color topaper coated with a mixture of kaolin and phenolic resin.

What is claimed is:

1. 6'-diethylamino-2-formylfiuoran.

2. 2-carbomethoxy-6'-diethylaminofluoran.

3. 2'-benzoyl-6'-diethylamino-4-methylfluoran.

References Cited UNITED STATES PATENTS 3,514,310 5/1970 Kimura et al.117-362 ALEX MAZEL, Primary Examiner ANNE MARIE T. TIGHE, AssistantExaminer US. Cl. X.R. 117-362, 36.8

